Tag: radar

In August, I wrote about how you can listen to meteors: radar bounced off their ion trail can be converted to sound, making eerie, creepy noises.

Via astronaut Ron Garan comes this video of recordings made by the U.S. Air Force Space Surveillance Radar in Texas during the Perseid meteor shower. It’s very, very cool:

As I wrote in the earlier post, here’s how this works:

You’re not really hearing sound, of course: meteors burn up in our atmosphere at a height of 100 km or so, too high to directly carry sound waves. But the Air Force has a radar surveillance facility in Texas that beams radio waves into the sky. When a bit of cosmic fluff streaks through our sky, the ionized trail it leaves reflects the radio waves, producing an echo. This radio wave is then translated into sound, so you can effectively hear a meteor!

… which is all well and good, but science aside, all I could think of while listening to that was the soundtrack to Ren and Stimpy walking along the landscape inside the hideous vortex of the black hole.

Sounds weird, but thanks to SpaceWeatherRadio, now you can! You’re not really hearing sound, of course: meteors burn up in our atmosphere at a height of 100 km or so, too high to directly carry sound waves. But the Air Force has a radar surveillance facility in Texas that beams radio waves into the sky. When a bit of cosmic fluff streaks through our sky, the ionized trail it leaves reflects the radio waves, producing an echo. This radio wave is then translated into sound, so you can effectively hear a meteor! Here’s an example of a Geminid meteor; it sounds like it could’ve been pulled right off the soundtrack for "Forbidden Planet". There’s also more info on how this works on the NASA science page.

If you want to listen live, here you go. I had it going for a while and heard several faint but distinct dying "Eeeeeeeoooooooo" sounds from meteors within a few minutes (as well as other sharper sounds I’m not sure I can identify, which makes the whole thing even cooler). The best time to listen for Perseids is after midnight Texas (Central) time, but if you leave it running you’re bound to hear a few of those creepy sounds coming from your speakers.

[This post is about the recent eruptions of Mt. Etna in Sicily. It’s part of a set of gorgeous images of volcanoes as seen from space; the first three are of Etna. Click the thumbnail picture to get a bigger picture and more information, and scroll through the gallery using the left and right arrows.]

Hartley 2 is a comet that is currently very close to the Earth as these things go: last week it passed us at a distance of about 18 million km (11 million miles). Astronomers took advantage of the close pass to ping the comet with radar pulses. By timing exactly how long it took the pulses to go from the telescope to the comet and back to Earth, they can create a map of the comet’s shape and other characteristics — something like how dolphins and bats use echolocation to map their surroundings… though, as Emily Lakdawalla at The Planetary Society Blog explains, it’s a bit more complicated.

From the images, it looks like the nucleus — the solid, central part of a comet — is highly elongated, about 2.2 km (1.4 miles) in length, and rotates once every 18 hours. We’ve only seen a handful of comets up close, and in general the nuclei are potato-shaped, so this one fits that description. The image has a scale of about 75 meters per pixel.

These observations were made to help out the EPOXI space mission, which will pass just 700 km (420 miles) from the nucleus of Hartley 2 on November 4. That means we’ll be getting some really cool close-up images and data from the comet very soon! Stay Tuned.